It probably is never a good idea to delete a project. For one thing, all associated data will also be erased like tasks, invoices, time recorded working on the project, etc. But since you are allowed to make a project you should also have the possibility to delete it. Deleting a project is the same as with other TUTOS entities. Just click on the 'Delete' link in the upper left part of the menu. A confirmation message box will pop up asking you if this is what you really want to do (see next picture). Just click on "OK" and you're ready.
The deletion confirmation message box